Failure of high dose 5-iodo-2'-deoxyuridine in the therapy of herpes simplex virus encephalitis. Evidence of unacceptable toxicity.

Two placebo-controlled double-blind studies were initiated to evaluate the therapeutic efficacy of 5-iodo-2-deoxyuridine (idoxuridine) in biopsy-provedcases of herpes simplex virus encephalitis. Twelve patients who on clinical grounds were thought to have herepes simplex virus encephalitis underwent brain biopsy; six of these patients were proved to have this disease, three were considered probable cases,and three were considered doubtful. The patients with proved or probably herpes simplex virus encephalitis were treated with parenteral idoxuridine (or placebo) at a dose of 100 mg per kiogram per day for five days. The occurrence of unacceptable myelosupperssion and the failure of idoxuridine therapy to prevent death led to the premature termination of both studies.